Question

Propose a mechanism for each of the following reactions:

Short answer

•H⁺ (an electrophile) binds to the most hydrogen-bonded sp² carbon of the alkene (a nucleophile).

• A protonated alcohol is formed when H₂O (a nucleophile) reacts with the carbocation (an electrophile).

• Because the pH of the solution is higher than the protonated alcohol's pKa, the protonated alcohol loses a proton.

Step-by-step solution

Mechanism for the acid-catalysed addition of water to an alkene-

•H⁺ (an electrophile) binds to the most hydrogen-bonded sp² carbon of the alkene (a nucleophile).

• A protonated alcohol is formed when H₂O (a nucleophile) reacts with the carbocation (an electrophile).

• Because the pH of the solution is higher than the protonated alcohol's pKa, the protonated alcohol loses a proton.

Mechanism for the addition of H-Cl to an alkene via an acid catalysed reaction

• H⁺ (the electrophile) adds to the most hydrogen-bonded sp² carbon.
• The nucleophile, CH₃OH, reacts with the carbocation to generate a protonated ether.
• Because the pH of the solution exceeds the protonated ether's pKa (pKa -3.6), the protonated ether loses a proton.